Can you use su and tu interchangeably?

Question

Can you use su and tu interchangeably?

Answer 1

La niña está jugando con tu perro would be grammatically incorrect.

No, it is not grammatically incorrect. Syntactically is correct.

La niña está jugando con tu perro - the girl is playing with your dog ( informal "you")

Now:

La niña está jugando con su perro, means:

the girl is playing with her (own) dog

the girl is playing with your dog (formal you/ tu = usted)

the girl is playing with his (John's) dog

the girl is playing with her dog ( a different female owner of the dog)

the girl is playing with your dog ( several owners of the dog)

It is all about context. To be able to understand which of the above meanings we are talking about, it is needed to have a previous statement. Example:

-Hey, ¿quién es el dueño del perro? / Hey, who owns the dog?

-Es John / John

-Mira: Lucy está jugando con su perro. ( El perro de John) / Look: Lucy is playing with his dog. ( John's dog)

Except for "your (plural formal) dog" and "their dog" that pretty much covers all the bases. - samdie, May 30, 2011

Answer 2

So, you are saying that you can't change it to "tu" in the following sentence:

La niña está jugando con su perro.

They are interchangeable for "your/yours", but obviously not for "his/hers/theirs".

Gracias!

Yes, on that case you can. But imagine this situation: There are a couple of kids playing and there is a woman standing next to the kids.... then you can ask both kids at the same time if the woman is their mother(using "su"). "¿Es ella su madre?" - fjfuentesh, May 29, 2011

If you say "Es ella tu madre" you will ask just to one of the kids! - fjfuentesh, May 29, 2011

ok... I think I got it. But if the girl was playing with HER OWN dog, what I said would be correct... right? - Tosh, May 29, 2011

Yes my friend! :) - fjfuentesh, May 29, 2011

Answer 3

I will take a stab at this answer...

Su is used in a more formal setting. Tu is used more informally.

¿Cuál es tu número de teléfono? you would ask to a friend or someone younger than you.

¿Cuál es su número de teléfono? you would ask to your boss, an older person, or someone that you would want to give respect to.

I may be wrong, but this is how I think about it as of now.

Su is used formally,not informally. Tu is, like you said, used for friends and younger people =) - Liger4S, May 29, 2011

Whoops! I fixed it... thanks! - Tosh, May 29, 2011

Answer 4

La niña está jugando con tu perro would be grammatically incorrect. Because you are speaking of another person, you must use the verb for the third person. Estás jugando con tu perro would be correct, as would ella está jugando con su perro but you cannot switch them up.

Answer 5

You are right Tosh. But you can't interchange those words in all cases, because "su" is a possesive adjetive.

In Spanish "su" is used for:

"su" = "your/yours"

"su" = "her"

"su" = "his"

"su/sus" = "their"

Answer 6

There are numerous threads on this topic, one as recent as yesterday link text